Need an excuse to treat yourself to dessert? A daily dose of chocolate or cocoa powder could help lower blood pressure, say the authors of a new systematic review by the Cochrane Library.

The review of 20 previous studies found that people who were given dark chocolate or cocoa powder daily showed a slight drop in blood pressure, compared with control groups. The studies were all short term — mostly lasting two to eight weeks — so it’s not clear how long the blood pressure benefits would last, but the “small reduction we saw over the short term might complement other treatment options and might contribute to reducing the risk of cardiovascular disease,” said lead researcher Dr. Karin Ried of the National Institute of Integrative Medicine in Melbourne, Australia, in a statement.

How does chocolate do its trick? It’s packed with compounds called flavanols — compounds like epicatechin, catechin and procyanidins, which are extracted from cacao beans and are thought to be responsible for the formation of nitric acid in the body. Nitric acid, in turn, serves to relax blood vessel walls and lower pressure.

High blood pressure is a key risk factor for heart disease, contributing to 47% of heart attacks and 54% of strokes worldwide, the authors write. They note that the risk of heart attack and stroke drops by about half for every 20 mm/Hg reduction in systolic blood pressure (the top number of your blood pressure reading) and 10 mm/Hg reduction in diastolic blood pressure (the bottom number).

The link between cocoa and blood pressure was first discovered among the Kuna Indians, a group of indigenous people living on San Blas Island off Panama, who drink three to four cups of cocoa a day. Kuna Indians who stayed on the island maintained a healthy blood pressure regardless of age, the authors report, while those who moved to the mainland — and consumed about 10 times less cocoa than their island-dwelling peers — showed age-related increases in blood pressure and rates of hypertension comparable to Western populations.

The trials included in the new review involved a total of 856 participants. The studies compared blood pressure outcomes among people eating high-flavanol cocoa products, low-flavanol products and products with no flavanols at all. Levels of flavanols can vary widely in chocolate, depending on its type and processing procedures. Fresh or fermented cocoa beans contain about 10% flavanols (100 mg per gram), for example, while the cocoa powder favored by Kuna Indians contains 3.6% flavanols and the typical cocoa-rich dark chocolate on the market contains 0.5%. Depending on how it’s processed, levels of flavanols in chocolate can drop down to 0.001%, or just 10 mg per 100 grams.

In the studies, 429 participants consumed between 3 and 100 g of cocoa or dark chocolate daily (the average Hershey bar is about 43 g), equal to about 30 to 1,080 mg of flavanols. The other 427 participants were in control groups eating low- or no-flavanol cocoa products.

Overall, people who ate chocolate and cocoa high in flavanols lowered their blood pressure by an average of 2 to 3 mm/Hg, compared with the control participants. When compared only with people eating flavanol-free products, the benefits were greater: people eating lots of flavanols had a 3 to 4 mm/Hg reduction in blood pressure. The difference between high- and low-flavanol groups was much less stark, and the researchers speculate that’s because even low-flavanol products may have a small, positive effect on blood pressure.

“Our results contribute to the evidence that dietary flavanoids found in cocoa, green tea, berries and red wine can play a role in cardiovascular risk factor reduction as part of a comprehensive lifestyle approach including regular exercise, healthy weight, and a balanced diet,” said Ried in an email.

In other words, you can’t substitute eating chocolate for good old-fashioned exercise and eating right (shucks) — but chocoholics will be glad to know that the study authors think moderate, regular consumption of flavanol-rich cocoa product could be a valid addition to a healthy lifestyle. “The reduction in blood pressure achieved with cocoa is somewhat comparable to other lifestyle modifications, such as diet and exercise (3-5 mm/Hg reduction), and may serve as complementary treatment option,” said Ried.

If you’re going to indulge, choose dark chocolate instead of milk. The study notes that dark chocolate contains more cocoa (50% to 80%), and therefore more flavanols, than milk chocolate (20% to 30%). And in general, milk chocolate is packed with a lot more sugar and fat, so its fattening qualities tend to outweigh its healthful ones. Bear in mind also that processing procedures can influence flavanol content, rendering levels different in chocolate bars from different companies, even if both are labeled has containing 70% cocoa.

Above all, don’t go overboard. As they say, everything in moderation — especially chocolate. “Smaller dosages may be as effective as larger dosages,” said Ried. “Larger daily intakes may not be as acceptable and practical.”